[AUDIO LOGO]
So let's jump in and take a closer look
at VPLS, or Virtual Private LAN Service.
The really cool advantage to this feature from a customer's
perspective is they really see the service provider's
environment as like one big Ethernet switch.
And that can be very advantageous for them
because everything's on one subnet then.
All of their routers can be OSPF neighbors with each other
or whatever routing protocol they're running and so on.
So let's, in this video, jump in and take a look
at the details of VPLS.
And then in the next video, we'll
be jumping onto the command line and putting this into action.
But for now, let's go ahead and jump in and take a look
at some of the details of VPLS.
So at its core, VPLS is a multipoint Ethernet connection
service.
So, essentially, what that means is
it gives us a way to connect remote sites together
as if they were connected to a single LAN
segment, so on the same VLAN or the same layer 2 connection.
And we can create either one or more emulated LANs
for each customer.
They might have a need to have different connections
effectively the same as having different VLANs.
Each of these emulated LANs is going to simply
look like a giant Ethernet switch
as far as the customer is concerned.
Again, just like on a regular Ethernet switch,
all of these devices will be able to talk to each other
at layer 2.
If we create numerous emulated LANs,
then they're going to be separate.
Again, much in the same way that VLANs would separate traffic,
the different emulated LANs are going
to separate the traffic as well.
For each of these LANs, the PE routers
are going to have a full mesh of pseudowires
because, of course, that's how this works.
So to keep the traffic separated,
we're going to have separate meshes of pseudowires.
Functionally speaking, when the PE receives a frame,
it will look at the destination MAC address
and forward it to the correct egress PE.
Now, that, of course, is going to bring up the question, well,
how does it know what is the correct egress PE?
And the answer to that is it learns the MAC addresses much
in the same way as a traditional switch would.
Initially, when we don't know any MAC addresses yet,
traffic is sent to all the pseudowires.
This is the equivalent of doing flooding
on a regular Ethernet switch.
Also just like a traditional switch,
we are then going to be learning as we're
forwarding traffic based on the source MAC addresses.
As traffic comes in, the source MAC is mapped to the interface
that it arrived on.
Now, that could either be a physical interface
if it's a locally connected device or a pseudowire if we're
learning it across the MPLS environment.
Once we've learned that, well, then traffic
can be forwarded just to the appropriate interface.
And, again, much like a traditional switch,
we are going to use split horizon to prevent loops.
Broadcast and multicast traffic are
going to be flooded to all of the sites and ports.
This, of course, is because we filter traffic based
on the destination MAC address.
And a broadcast MAC address or a multicast MAC address
will never be the source.
And since it's not the source, that means we never learn it.
And if we never learn it, then we
can't filter based on that address.
So, therefore, it's going to get flooded.
That means that we're going to be relying on split horizon
once again to make sure that we're forwarding this
across a loop-free tree and not actually looping our broadcast
or multicast traffic.
Now, on the customer side, the CE device
can actually be a switch or a router.
Generally speaking, we would prefer
the customer use a router.
This is going to be recommended.
Now, here, we say in a larger environment.
But, honestly, really in any environment,
if they can use a router, that would be preferred.
And the reason for that is we wouldn't
have to learn all those MAC addresses on the PEs.
Otherwise, potentially, the PEs may
have to learn every MAC address in the customer's network.
If there's a router between, then we just
have to learn the MAC address of the router.
So in this video, we got some more detailed information
on how VPLS works, how it acts as a switch for the customer,
and how it actually handles the forwarding of traffic,
both if we have a single emulated LAN
or if we have more than one.
Now, of course, it's time to actually implement this and get
it working.
And that's exactly what we get to do next.
Until then, I hope this has been informative for you.
And I'd like to thank you for viewing.